Many flying noxious insects such as mosquitos not only cause annoyance to humans when bitten by such insects, the venoms of these insects can cause skin irritations and inflammation in the mildest case, to stings causing severe allergic reaction such as anaphalactic shock if not treated quickly. The insects may also be carriers of infectious diseases such as malaria, typhoid, yellow fever, cholera and West Nile virus that could be fatal to humans. The disease or virus is passed on to humans upon being bitten by the insects infected with such disease or virus.
Numerous methods and devices have been developed for repelling annoying insects or for decimating them so as to prevent them from biting humans. A well known method is by burning an incense which produces a poisonous smoke that would repel or kill the insects; however, such method is rather ineffective and the smoke may also be harmful to humans. Another method is by producing a high frequency sound which is audible to the annoying insects and yet not audible to humans. This sound duplicates the sound of the predators of the insects. The sound is broadcast over a wide area of space around the humans so that it would drive the noxious insects away from the area upon sensing the presence of their predators. However, this method is also found to be ineffective.
An effective method of eliminating noxious insects in an area is by spraying insecticide. However, the insecticide spray would cause pollution to the natural environment and it may also cause harmful effects to humans as well.
Applying insect repelling oil, ointment or spray directly on exposed skin is another effective way of repelling noxious insects, but again the oil or ointment or spray may cause skin irritation and discomfort, and they may also cause harmful effect to human health with long term use.